Lecture 3 - overview of methods

Question 1

How do we classify neurons?

Answer 1

• structure
• gene expression

Question 2

How do we base the structure of neurons to classify them?

Answer 2

• number of neurites
• dendritic geometry - unipolar, bipolar & multipolar
• connections - where do they project?
• axon length

Question 3

How do we base gene expression of neurons to classify them?

Answer 3

• underlies structural differences
• defines neurotransmitter expression - e.g. excitatory vs inhibitory neurotransmitters

This is useful as neurons can be identified, which reduces the need for tracing of each neuron individually.

Question 4

What is a ganglia?

Answer 4

clump of cell body in the peripheral system

Question 5

What is the role of dorsal root ganglion?

Answer 5

transmit signal from sensory receptors, however it becomes a dendrite. Signal carried to spinal cord.
- the lack of branching means it is RELIABLE at transferring information

Question 6

How many neurites do dorsal root ganglion have?

Answer 6

1 - unipolar

Question 7

Describe the properties of bipolar neurites

Answer 7

• small area for receiving synaptic input = highly specialised function
• reliable relay of information
• retinomal bipolar

Question 8

Describe the properties of multipolar neurites

Answer 8

• can receive about 150,000 connections
• majority of neurons in the brain
• large area for receiving synaptic input
• high levels of convergence
• involved in motor control

Question 9

What are the 2 types of dendritic geometry?

Answer 9

• Stellate
• Pyramidal

Question 10

Describe stellate dendritic geometry

Answer 10

star shaped dendritic arbour

Question 11

Describe pyramidal dendritic geometry

Answer 11

• distinct APICAL & BASAL dendritic trees
• pyramidal shaped soma
• found in the cerebral cortex

Question 12

Where do sensory neurons project to?

Answer 12

afferent

Question 13

Where do motor neurons project to?

Answer 13

efferent

Question 14

What are 2 types of interneurons?

Answer 14

• relay or projection neurons
• long interneurons

Question 15

What do relay or projection neurons do?

Answer 15

• connect brain regions
• can be quite long

Question 16

What do local interneurons do?

Answer 16

• process information in local circuits
• short axons

Question 17

What allows investigation into where neurons and what they are doing?

Answer 17

manipulation of neuron genetics can lead to fluorescence (inclusion of gene/promoter region) or knocking out a gene

Question 18

What acts as nerve glue and fills the space around neurons?

Answer 18

Glia
- extracellular space of approx. 20um between glia & neurons
- can proliferate throughout life

Question 19

Can glia cells regenerate?

Answer 19

yes - whereas neurons can’t in lots of regions

Question 20

What are glial cells found in the CNS involved in homeostasis called?

Answer 20

astrocytes

Question 21

What are glial cells found in the PNS involved in homeostasis called?

Answer 21

satellite cells

Question 22

What are glial cells in the CNS involved in myelinating cells called?

Answer 22

oligodendrocytes

Question 23

What are glial cells in the PNS involved in myelinating cells called?

Answer 23

Schwaan cells

Question 24

What are glial cells in the CNS that act as phagocytic cells?

Answer 24

microglia

Question 25

What are glial cells in the PNS that act as phagocytic cells?

Answer 25

Schwaan cells & macrophages

Question 26

What are astrocytes?

Answer 26

• control environment surrounding neurons
• spatial domains
• unique marker - glial fibrillation acidic protein (GFAP) - immunohistochemistry can be used to visualise astrocytes
• many subtypes

Question 27

How do astrocytes as fuel suppliers?

Answer 27

• glycogen stores of the brain
• 5-10 minutes supply
• metabolise glycogen & supply lactate
• endfeet rake up glucose

Question 28

What occurs during times of lower glucose levels?

Answer 28

neurons may use the glycogen stores in astrocytes to create ATP.

Question 29

What does the tripartite synapse do?

Answer 29

• terminates neurotransmitter activity
• recycles neurotransmitter to presynaptic terminals
• astrocytes have receptors too

Question 30

What makes up the tripartite synapse?

Answer 30

• presynaptic terminal
• dendrites
• glial cells (astrocytes)

Question 31

What are other roles of astrocytes?

Answer 31

• buffer extracellular potassium
• form part of the blood brain barrier
• couple neuronal activity to blood supply

Question 32

What is microglia?

Answer 32

macrophages of the CNS (phagocytic)
- can be in an active or inactive form
- key role in tissue surveillance & phagocytosis
- many more roles - emerging field
- can have harmful roles in neurodegenerative diseases

Question 33

What do oligodendrocytes do?

Answer 33

• myelinating oligodendrocytes from myelin sheaths of CNS axons
• can have 15-30 projections from cell body to myelin sheath

Question 34

What do Schwaan cells do?

Answer 34

• form myelin sheaths of PNS (peripheral nervous system)
• one Schwaan cell provides one myelin segment to a single axon

Question 34

Describe the formation of myelin sheath

Answer 34

• process of oligo cytoplasm
• wraps many times around the axon
• cytoplasm squeezed out of layers by COMPACTION - left with membrane
• myelin still a living component - mainly made of membrane

Question 35

Why do myelin sheaths maintain contact glial cells?

Answer 35

for nourishment

Question 36

What is the function of myelin?

Answer 36

• myelination is insulating & creates nodes of Ranvier enabling saltatory conduction